Circuit board capable of preventing electrostatic breakdown and magnetic head using the same

ABSTRACT

The invention provides a magnetic head capable of positively preventing electrostatic breakdown of an MR magnetic head device, and a method of manufacturing the magnetic head. A circuit board comprises at least a pair of leads for constructing a circuit, lands connected respectively to the leads, and solder bumps formed respectively on the lands. The solder bumps are arranged in an adjacent relationship and, when the solder bumps are crushed, peripheral portions of the solder bumps are pressed or spread so as to overlap with each other. The magnetic head includes the circuit board.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a circuit board, and a magnetichead incorporating the circuit board. More particularly, the presentinvention relates to a circuit board capable of protecting an MRmagnetic head device, which incorporates the circuit board, againstelectrostatic breakdown.

[0003] 2. Description of the Related Art

[0004] An example of a conventional magnetic head 201 for use in acomputer hard disk is shown in FIG. 17. The magnetic head 201 generallycomprises a slider 203, a load beam 202, and a circuit board 204. Theslider 203 is attached to a fore end 202 a of the load beam 202 througha flexure, and a base plate 209 is attached to an opposite end 202 b ofthe load beam 202. The circuit board 204 is attached to the base plate209.

[0005] The slider 203 includes an MR magnetic head device 208 forreproducing magnetically recorded data, and an inductive head device(not shown) for recording data to be magnetically recorded. From each ofthese head devices, two lead lines are extended to transmit and receivea reproduced signal and a recording signal to and from the outside ofthe magnetic head. These four lead lines 205 a, 205 b, 206 a, 206 b areconnected to the circuit board 204 at the side of the base plate 209where it is attached to the opposite end 202 b of the load beam 202.

[0006] The circuit board 204 is formed of a flexible printed board, andincludes four leads 215 a, 215 b, 216 a, 216 b connected respectively tothe lead lines extended from the head devices (i.e. , 205 a, 205 b, 206a, 206 b). Mounting terminals 215 c, 215 d, 216 c, 216 d are providedrespectively midway on the leads 215 a, 215 b, 216 a, 216 b. Inspectionterminals 215 e, 215 f, 216 e, 216 f are provided respectively at endsof the leads 215 a, 215 b, 216 a, 216 b.

[0007] The leads 215 a, 215 b, that are connected to the lead lines 205a, 205 b of the MR magnetic head device 208, include lands 223, 224provided between the mounting terminals 215 c, 215 d and the inspectionterminals 215 e, 215 f, respectively.

[0008] In a conventional magnetic head of this type, the circuitincluding the MR magnetic head device 208 is typically constructed as aclosed circuit by attaching a shunt clip or forming a bonding wirebetween the lands 223, 224 so as to short the lands 223, 224 together.This is done to prevent electrostatic breakdown of the MR magnetic headdevice 208 during a period from manufacture of the magnetic head toassembly thereof into a hard disk drive.

[0009] This may result in a number of problems. For example, when thelands 223, 224 are shorted together by using a clip, there is a riskthat the clip may slip off as result of vibration during transport ofthe magnetic head. As a result, the MR magnetic head device 208 maysuffer electrostatic breakdown.

[0010] Also, shorting the lands 223, 224 together by wire bondingrequires that a wire-bonding step be included in the manufacturingprocess of the magnetic head, thereby resulting in an increasedproduction cost of the magnetic head.

[0011] In view of the state of the art set forth above, an object of thepresent invention is to provide a magnetic head capable of positivelypreventing electrostatic breakdown of an MR magnetic head device, and amethod of manufacturing the magnetic head, that overcomes theabove-identified problems.

SUMMARY OF THE INVENTION

[0012] The present invention is directed to a circuit board comprisingat least a pair of leads for constructing a circuit, lands connectedrespectively to the pair of leads, and solder bumps formed respectivelyon the lands, wherein the solder bumps are arranged in an adjacentrelationship. The solder bumps are subsequently crushed, causingperipheral portions of the solder bumps to spread and overlap with eachother.

[0013] The present invention is also directed to a circuit boardcomprising at least a pair of leads for constructing a circuit, landsformed for connection respectively to the pair of leads, and a solderbridge for electrically interconnecting the lands, wherein the solderbridge is formed by peripheral portions of the solder bumps formed onthe lands so that portions of the solder bumps overlap with each other.Preferably, the solder bridge is formed by crushing the solder bumpsformed on the lands to an extent that crushed peripheral portions of thesolder bumps are overlapped with each other.

[0014] Consequently, the leads constructing the circuit on the circuitboard can be easily shorted together by crushing the solder bumps, andthe circuit can be formed into a closed circuit.

[0015] Moreover, since the solder bridge is formed by the peripheralportions of the solder bumps which are integrally overlapped with eachother, the contact area between the solder bumps is increased and theleads can be positively shorted between them.

[0016] Further, the present invention is directed to a circuit shortingmethod for a circuit board comprising at least a pair of leads forconstructing a circuit, lands connected respectively to the pair ofleads, and solder bumps formed on the lands and positioned adjacent toeach other. The method comprises the steps of crushing one of the solderbumps such that a peripheral portion of the one solder bump is pressedto spread outward in a radial direction to approach the other solderbump; and then crushing the other solder bump such that a peripheralportion of the other solder bump is pressed to spread outward in aradial direction to contact with the peripheral portion of the onesolder bump, whereby the pair of leads are shorted.

[0017] With this circuit shorting method, two solder bumps are contactedwith each other by crushing the solder bumps one by one. Therefore, thesolder bumps can be each positively crushed to make the leads shortedbetween them, and the circuit can be positively formed into a closedcircuit.

[0018] In the above circuit shorting method, the step of crushing theother solder bump is preferably performed until a part of the peripheralportion of the other solder bump overlaps the peripheral portion of theone solder bump.

[0019] One feature of this circuit shorting method is that the pair ofsolder bumps are contacted with each other in an overlapping relation.Thus, the solder bumps are unlikely to be separated, even when thecircuit board is bent or flexed. Further, a contact area between thesolder bumps is increased and the pair of leads can be positivelyshorted between them.

[0020] In the above circuit shorting method, the solder bumps arepreferably each crushed under heating. Heating of the solder bumpscauses them to soften, thereby reducing the load required for crushingthe solder bumps, and the solder bumps can be positively crushed withoutdamaging the circuit board itself.

[0021] In the above circuit shorting method, the pair of solder bumpsmay be crushed simultaneously underheating. Crushing the solder bumpssimultaneously, while being softened under heating, reduces the loadrequired for crushing the solder bumps, and the pair of solder bumps canbe positively contacted with each other even when they are crushedsimultaneously. Additionally, damage of the circuit board itself can beavoided.

[0022] In the above circuit shorting method, the solder bumps arepreferably each crushed under heating and rubbing. By heating andrubbing the solder bumps, each solder bump is caused to spread in theplanar direction of the circuit board while being crushed. This causesthe solder bumps to be more positively contacted with each other.

[0023] The present invention is directed to a magnetic head in which aslider including an MR magnetic head device is attached to a fore end ofa load beam, a circuit board is attached to an opposite end of the loadbeam, and a pair of lead lines extended from the MR magnetic head deviceare connected to the circuit board. The circuit board comprises at leasta pair of leads connected respectively to the lead lines andconstructing a circuit including the MR magnetic head device incooperation with the lead lines, lands connected respectively to theleads, and solder bumps formed respectively on the lands. The solderbumps are arranged in an adjacent relationship and, when the solderbumps are crushed, peripheral portions of the solder bumps are pressedto spread and overlap with each other.

[0024] The present invention is also directed to a magnetic head inwhich a slider including an MR magnetic head device is attached to afore end of a load beam, a circuit board is attached to an opposite endof the load beam, and a pair of lead lines extended from the MR magnetichead device are connected to the circuit board. The circuit boardcomprises at least a pair of leads connected respectively to the leadlines and constructing a circuit including the MR magnetic head devicein cooperation with the lead lines, lands connected respectively to theleads, and a solder bridge for electrically interconnecting the lands.The solder bridge is formed by peripheral portions of the solder bumpsformed respectively on the leads and overlapped with each other. Thesolder bridge is preferably formed by crushing the solder bumps formedon the lands to an extent that crushed peripheral portions of the solderbumps are overlapped with each other.

[0025] With respect to the MR magnetic head device, a circuit isconstructed with the lead lines extended from the head device and thepair of leads connected to the lead lines. The circuit can be easilyformed into a closed circuit by crushing the solder bumps so that thepair of leads are shorted between them. As a result, the MR magnetichead device can be protected against electrostatic breakdown.

[0026] The present invention is directed to a method of manufacturing amagnetic head in which a slider including an MR magnetic head device isattached to a fore end of a load beam and a circuit board is attached toan opposite end of the load beam. The circuit board comprises at least apair of leads connected to the MR magnetic head device, lands connectedrespectively to the pair of leads, and solder bumps formed respectivelyon the lands and positioned adjacent to each other The method comprisesthe steps of crushing one of the solder bumps such that a peripheralportion of the one solder bump is spread outward in a radial directionto approach the other solder bump; and then crushing the other solderbump such that a peripheral portion of the other solder bump is likewisespread outward in a radial direction to contact with the peripheralportion of the one solder bump, whereby the pair of leads are shorted.

[0027] With this method of manufacturing a magnetic head, a circuit isconstructed by the MR magnetic head device, the lead lines extended fromthe head device and the pair of leads connected to the lead lines. Thecircuit is formed into a closed circuit by crushing the solder bumps sothat the pair of leads are shorted between them. Therefore, the MRmagnetic head device can be protected against electrostatic breakdown.

[0028] In the above method of manufacturing a magnetic head, the step ofcrushing the other solder bump is preferably performed until a part ofthe peripheral portion of the other solder bump overlaps the peripheralportion of the one solder bump. Since the pair of solder bumps arecontacted with each other in an overlapping relationship, the contactarea between the solder bumps is increased and the pair of leads can bemore positively shorted together, whereby the circuit including the MRmagnetic head device can be formed into a closed circuit.

[0029] In the above described method of manufacturing a magnetic head,the solder bumps are each preferably crushed under heating. Heatingsoftens the solder bumps, thereby reducing the load required forcrushing the solder bumps, and the solder bumps can be crushed withoutdamaging the circuit board itself.

[0030] In the above described method of manufacturing a magnetic head,the pair of solder bumps may be crushed simultaneously under heating.Crushing the solder bumps simultaneously while they are being softenedunder heating, reduces the load required for crushing the solder bumps,and the pair of solder bumps can be positively contacted with each othereven when they are crushed simultaneously. Damage of the circuit boardcan consequently be avoided.

[0031] In the above described method of manufacturing a magnetic head,the solder bumps are each preferably crushed under heating and rubbing.By heating and rubbing the solder bumps as they are each crushed, eachsolder bump is spread in the planar direction of the circuit board whilebeing crushed, which causes the solder bumps to be more positivelycontacted with each other.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is a perspective view of a magnetic head according to anembodiment of the present invention;

[0033]FIG. 2 is a plan view showing a principal part of a circuit boardprovided on the magnetic head shown in FIG. 1;

[0034]FIG. 3 is a sectional view of the principal part of the circuitboard shown in FIG. 2;

[0035]FIG. 4 is a plan view showing the principal part of the circuitboard provided on the magnetic head shown in FIG. 1;

[0036]FIG. 5 is a sectional view of the principal part of the circuitboard shown in FIG. 4;

[0037]FIG. 6 is a sectional view depicting a step of a method ofmanufacturing the magnetic head according to an embodiment of thepresent invention;

[0038]FIG. 7 is a sectional view depicting a step of a method ofmanufacturing the magnetic head according to the embodiment of thepresent invention;

[0039]FIG. 8 is a sectional view depicting a step of a method ofmanufacturing the magnetic head according to the embodiment of thepresent invention;

[0040]FIG. 9 is a sectional view depicting a step of a first alternativemethod of manufacturing the magnetic head according to an embodiment ofthe present invention;

[0041]FIG. 10 is a sectional view depicting a step of the firstalternative method of manufacturing the magnetic head according to theembodiment of the present invention;

[0042]FIG. 11 is a sectional view depicting a step of the firstalternative method of manufacturing the magnetic head according to theembodiment of the present invention;

[0043]FIG. 12 is a sectional view depicting a step of a secondalternative method of manufacturing the magnetic head according to anembodiment of the present invention;

[0044]FIG. 13 is a sectional view depicting a step of the secondalternative method of manufacturing the magnetic head according to theembodiment of the present invention;

[0045]FIG. 14 is a graph showing changes in the diameter of a solderbump when the solder bump is crushed pursuant to an embodiment of thepresent invention;

[0046]FIG. 15 is a graph showing changes in the diameter of a solderbump when the solder bump is crushed pursuant to an embodiment of thepresent invention;

[0047]FIGS. 16a-d are schematic views showing a pair of solder bumps insuccessive states when crushed pursuant to an embodiment of the presentinvention;

[0048]FIG. 17 is a perspective view of a conventional magnetic head.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] Embodiments of the present invention will be described below withreference to the drawings.

[0050]FIG. 1 shows a magnetic head 1 according to the present invention.The magnetic head 1 mainly comprises a load beam 2, a slider 3 attachedto a fore end 2 a of the load beam 2, and a circuit board 4 of thepresent invention attached to a base plate 9. The base plate 9 isattached to a base (opposite) end 2 b of the load beam 2.

[0051] The slider 3 includes an MR magnetic head device 8 serving as areproducing head and an inductive head device (not shown) serving as arecording head, these head devices being provided on one end surface ofthe slider 3.

[0052] One pair of lead lines 5 a, 5 b are extended from the MR magnetichead device 8, and another pair of lead lines 6 a, 6 b are extended fromthe inductive head device.

[0053] The lead lines 5 a, 5 b, 6 a, 6 b are collected together by aflexible printed circuit (FPC) board 7 on the upper surface of the loadbeam 2. The FPC board 7 extends to the base plate 9 (attached to theopposite end 2 b of the load beam 2).

[0054] The circuit board 4 is connected to the FPC board 7 throughconnection terminals 17 a, 17 b, 18 a, 18 b. The circuit board 4 isattached to the base plate 9 in an overlapped relationship to an endportion of the FPC board 7.

[0055] The circuit board 4 of the present invention comprises, as shownin FIGS. 1 to 3, a substrate 21 and an insulating layer 22 formed overthe substrate 21. Four leads 15 a, 15 b, 16 a, 16 b are formed on thesubstrate 21 and are covered by the insulating layer 22. Also, as shownin FIG. 1, the leads 15 a, 15 b, 16 a, 16 b are connected to theconnection terminals 17 a, 17 b, 18 a, 18 b, respectively.

[0056] Further, as shown in FIG. 1, the leads 15 a, 15 b, 16 a, 16 binclude mounting terminals 15 c, 15 d, 16 c, 16 d and inspectionterminals 15 e, 15 f, 16 e, 16 f provided thereon.

[0057] At the juncture (i.e., overlapped portion) between the circuitboard 4 and the FPC board 7, the connection terminals 17 a, 17 b, 18 a,18 b of the circuit board 4 are connected respectively to fourconnection terminals (not shown) of the FPC board 7.

[0058] As set forth in the above-described arrangement, the lead 15 a isconnected to the lead line 5 a through the connection terminal 17 a, andthe lead 15 b is connected to the lead line 5 b through the connectionterminal 17 b. Similarly, the lead 16 a is connected to the lead line 6a through the connection terminal 18 a, and the lead 16 b is connectedto the lead line 6 b through the connection terminal 18 b.

[0059] Thus, the MR magnetic head device 8, the lead lines 5 a, 5 b andthe leads 15 a, 15 b cooperatively construct or form a circuit.

[0060] Lands 23, 24 are formed on the leads 15 a, 15 b (which forms thecircuit including the MR magnetic head device 8) between the mountingterminals 15 c, 15 d and the inspection terminals 15 e, 15 f,respectively, as shown in FIGS. 2 and 3. Solder bumps 25, 26, beingsubstantially circular in plan view, are formed on the lands 23, 24,respectively. The lands 23, 24 are formed as conductors positioned onthe leads 15 a, 15 b, and projecting through the insulating layer 22.The solder bumps 25, 26 are formed respectively on the lands 23, 24 andare electrically connected to the leads 15 a, 15 b.

[0061] In the preferred embodiment, the solder bumps 25, 26 are formedfrom a solder made of, e.g., an SnPb alloy, and has a melting pointpreferably in the range of about 180° C.-185° C., taking into accountthat the solder bump is required to be easily crushed.

[0062] The solder bumps 25, 26 are preferably arranged adjacent to eachother and with a distance left between them that, when crushed, theirperipheral portions 25 a, 26 a are spread outward in the radialdirection to allow interconnection between the solder bumps 25 and 26.More specifically, assuming that the solder bumps 25, 26 each have adiameter of 0.29-0.34 mm, the center-to-center distance between thesolder bumps 25 and 26 is preferably in the range of 0.39-0.41 mm. Ifthe center-to-center distance is less than 0.39 mm, there is a risk thatthe solder bumps 25, 26 may contact with each other when they areformed. Conversely, if the center-to-center distance is more than 0.41mm, there is a risk that the solder bumps 25, 26 may not contact witheach other even after they are crushed.

[0063]FIGS. 4 and 5 show the solder bumps 25, 26 of the circuit board 4after being crushed according to the present invention. When the solderbumps 25, 26 are crushed, the peripheral portions 25 a, 26 a of thesolder bumps 25, 26 are caused to spread into an integrally overlappedrelationship, thereby forming a solder bridge 125. The solder bridge 125electrically connects the lands 23, 24 to each other for the purpose ofshorting the leads 15 a, 15 b together so that the circuit including theMR magnetic head device 8 is formed into a closed circuit.

[0064] A method of manufacturing the magnetic head of the presentinvention will now be described with reference to the drawings.

[0065] First, the slider 3, including the MR magnetic head device 8 andthe inductive head device (not shown), is attached to the fore end 2 aof the load beam 2. The lead lines 5 a, 5 b, 6 a, 6 b are extended fromthe MR magnetic head device 8 and the inductive head device up to thebase end 2 b of the load beam 2 through the FPC board 7.

[0066] Then, the circuit board 4 is attached to the base end 2 bof theload beam 2. At this time, the lead lines 5 a, 5 b, 6 a, 6 b areconnected to the leads 15 a, 15 b, 16 a, 16 b, respectively, of thecircuit board 4 through the connection terminals 17 a, 17 b, 18 a, 18 b.Accordingly, the MR magnetic head device 8, the lead lines 5 a, 5 b andthe leads 15 a, 15 b are interconnected to form or construct a circuit.

[0067] Then, as shown in FIG. 6, a pressing tip 30 is prepared andpressed against the first solder bump 25, whereupon the solder bump 25is crushed as shown in FIG. 7. As a result of this crushing, theperipheral portion 25 a of the solder bump 25 is pressed or spreadoutward in the radial direction so as to approach the other or secondsolder bump 26.

[0068] Then, as shown in FIG. 8, the pressing tip 30 is pressed againstthe other or second solder bump 26, whereupon the solder bump 26 iscrushed. The peripheral portion 26 a of the solder bump 26 is therebypressed or spread outward in the radial direction until the peripheralportion 26 a overlaps the peripheral portion 25 a of the first solderbump.

[0069] When the solder bumps 25, 26 contact with each other, the leads15 a, 15 b are shorted together or between them and the circuitincluding the MR magnetic head device 8 is formed into a closed circuit.

[0070] An alternative method for crushing the solder bumps 25, 26 isshown in FIGS. 9-11. Instead of the pressing tip 30 (as describedabove), a heater tip 33 comprising a heat-resistant resin film 31 and aheater 32 attached to the film 31 is utilized. The heater tip 33 ispressed against the first solder bump 25 while heating the same,whereupon the solder bump 25 is crushed as shown in FIG. 10. As a resultof the crushing, the peripheral portion 25 a of the solder bump 25 ispressed or spread outward in the radial direction so as to approach theother or second solder bump 26.

[0071] Then, as shown in FIG. 11, the heater tip 33 is pressed againstthe other or second solder bump 26 while heating the same, whereupon thesolder bump 26 is crushed. The peripheral portion 26 a of the solderbump 26 is thereby pressed or spread outward in the radial directionuntil the peripheral portion 26 a overlaps the peripheral portion 25 aof the first solder bump 25.

[0072] As the solder bumps 25, 26 contact each other, the leads 15 a, 15b are shorted together or between them, and the circuit including the MRmagnetic head device 8 is formed into a closed circuit.

[0073] In the case of crushing the solder bumps 25, 26 by the heater tip33, it is preferable that the heating temperature of the solder bumps25, 26 be set to 170-210° C., and more preferably 175-185° C. Thepreferred heating time is 1.5-2.5 seconds, and more preferably 1.5-2.0seconds.

[0074] If the heating temperature is lower than 170° C., then the soldermay not be sufficiently softened, thereby preventing the solder bumps25, 26 from contacting with each other, or that a too large of a loadmust be applied to crush the solder bumps 25, 26, which can cause thecircuit board 4 to be damaged. If the heating temperature is higher than210° C., then there is a risk that the solder bumps 25, 26 arecompletely melted into a liquid state, and when crushed, parts of thesolder may scatter around the solder bumps 25, 26 upon collapse of thebump shapes.

[0075] Further, if the heating time is shorter than 1.5 seconds, thereis a risk that the solder will not be sufficiently softened to permitthe solder bumps 25, 26 to contact with each other upon crushing. If theheating time is longer than 2.5 seconds, then there is a risk that thesolder bumps 25, 26 will completely melted into a liquid state, and whencrushed, parts of the solder may scatter around the solder bumps 25, 26upon collapse of the bump shapes.

[0076] Another alternative method for crushing the solder bumps 25, 26is shown in FIGS. 12-13. A pressing tip 35 that is larger than thepressing tip 30 described above is utilized in conjunction with a heater34. The heater 34 is held in contact with the underside of the circuitboard 4 to heat the solder bumps 25, 26. The pressing tip 35 ispositioned above the circuit board 4. Then, as shown in FIG. 13, boththe solder bumps 25, 26 are crushed simultaneously by the pressing tip35 while they are heated from below with the heater 34.

[0077] In this case, the peripheral portion 25 a of one solder bump 25and the peripheral portion 26 a of the other solder bump 26 aresimultaneously pressed or spread outward in the radial direction so asto approach and contact with each other. As the solder bumps 25, 26contact with each other, the leads 15 a, 15 b are shorted together orbetween them and the circuit including the MR magnetic head device 8 isformed into a closed circuit.

[0078] When crushing the solder bumps 25, 26 by the larger pressing tip35 and the heater 34, the heating temperature and the heating time arepreferably set in accordance with the above-described methods.

[0079] Moreover, when crushing the solder bumps 25, 26 by any of theabove-described methods (i.e., with the pressing tip 30, the heater tip33, or the combination of the pressing tip 35 and the heater 34, asshown in FIGS. 6 to 13), the solder bumps 25, 26 are preferably crushedwhile the tips 30, 33, or 35 are moved in a rubbing fashion with respectto the solder bumps in the planar direction of the circuit board 4. Thisrubbing improves or increases the spreading of the solder bumps 25, 26in the planar direction of the circuit board 4 during the step ofcrushing, thereby increasing the positive contacted between the solderbumps 25, 26.

[0080] With the magnetic head 1 described above, the MR magnetic headdevice 8, the lead lines 5 a, 5 b and the leads 15 a, 15 b cooperativelyconstruct a circuit, and one pair of the solder bumps 25, 26 connectedto the leads 15 a, 15 b are crushed successively or simultaneously so asto contact with each other. The leads 15 a, 15 b are thereby shortedbetween them to make the constructed circuit become a closed circuit. Asa result, the MR magnetic head device 8 can be protected againstelectrostatic breakdown.

[0081] With the above-described method of manufacturing the magnetichead 1, the circuit including the MR magnetic head device 8 can beeasily formed into a closed circuit by merely crushing the solder bumps25, 26.

[0082] Also, with the above-described method of manufacturing themagnetic head 1, the solder is softened by heating when the solder bumps25, 26 are crushed. Therefore, the load required for crushing the solderbumps 25, 26 is reduced and the solder bumps 25, 26 can be positivelycrushed without damaging the circuit board 4.

[0083] Further, since the solder bumps 25, 26 are crushed to an extentthat a part of the peripheral portion 26 a of the other solder bump 26overlaps the peripheral portion 25 a of one solder bump 25, the contactarea between the solder bumps 25, 26 is increased and one pair of theleads can be more positively or securely shorted together or betweenthem. As a result, the circuit including the MR magnetic head device 8can be formed into a closed circuit. Since the peripheral portions 25 a,26 a are overlapped with each other, the solder bumps 25, 26 are avoidedfrom separating off, for example, even when the circuit board 4 is bent.

[0084] Furthermore, with the above-described method of manufacturing themagnetic head 1 by crushing one pair of the solder bumps 25, 26 whilebeing heated, the load required for crushing the solder bumps 25, 26 isreduced and the solder bumps 25, 26 can be positively contacted witheach other even though both the solder bumps are crushed at the sametime, without damaging the circuit board 4 when the solder bumps arecrushed.

[0085] In addition, with the above-described method of manufacturing themagnetic head 1 by crushing the solder bumps 25, 26 in a rubbingfashion, the solder bumps 25, 26 are pressed or spread in the planardirection of the circuit board 4 while being crushed and they can bemore positively contacted with each other.

EXPERIMENTAL EXAMPLE 1

[0086] A land was formed on a circuit board, and a substantiallysemispherical solder bump having a diameter of 0.32 mm (320 μm) and amaximum height of 28 μm was formed on the land.

[0087] Further, on another circuit board, a substantially semisphericalsolder bump having a diameter of 0.26 mm (260 μm) and a maximum heightof 25 μm was formed in a similar manner to the above. The solder usedwas made of an SnPb alloy and had the melting point of 183° C.

[0088] These solder bumps were each crushed by applying a load of 5-15kgf, and changes in the bump diameter were measured. Measured resultsare shown in FIGS. 14 and 15.

[0089] As seen from FIG. 14, the diameter of the solder bump having adiameter of 320 μm was changed to 450-490 μm after the crushing.

[0090] Also, as seen from FIG. 15, the diameter of the solder bumphaving a diameter of 260 μm was changed to 370-430 μm after thecrushing.

[0091] It is thus understood that, when the solder bump is crushed, thebump diameter is increased and a peripheral portion of the solder bumpis pressed or spread outward in the radial direction.

EXPERIMENTAL EXAMPLE 2

[0092] Next, a circuit board including one pair of solder bumps, asshown in FIGS. 1 to 3, was fabricated. The solder bumps each had adiameter of 0.32 mm and the center-to-center distance between the solderbumps was 0.4 mm. The solder used was made of an SnPb alloy and had amelting point of 183° C.

[0093] First, one solder bump was crushed by heating the solder bump upto 220-260° C. for 1.0-2.5 seconds, under a load of 8 kgf with a heatertip, while the heater tip was moved in rubbing fashion in the planardirection of the circuit board. The other solder bump was then crushedin a similar manner.

[0094] Continuity between both the solder bumps was subsequentlychecked. Checked results are listed in Table 1 and shown schematicallyin FIGS. 16a-d. FIGS. 16a-d shows the solder bumps in successive stateswhen crushed while being heated to a temperature of 250° C.

[0095] As seen from Table 1 and FIG. 16a, when the heating time is 1.0second at the heating temperature in the range of 170-250° C., thesolder bumps are insufficiently crushed and they do not contact witheach other. Thus, no electrical conduction is established between thesolder bumps.

[0096] As seen from FIG. 16d, when the heating temperature is higherthan 210° C. and the heating time is longer than 2.5 seconds, the soleris excessively melted and a part of the solder is scattered around thesolder bumps.

[0097] From the above results, it is understood that in order to crushand contact one pair of the solder bumps each having the diameter of0.32 mm with the center-to-center distance of 0.4 mm, the solder bumpsare preferably crushed while being heated to 170-210° C. for 1.5-2.0seconds (see FIGS. 16b-c) TABLE 1 Heating Time Heating Temperature (°C.) (sec) 170° C. 180° C. 190° C. 200° C. 210° C. 1.0 sec no no no no noconduction conduction conduction conduction conduction 1.5 secconduction conduction conduction conduction conduction 2.0 secconduction conduction conduction conduction conduction 2.5 secconduction conduction conduction conduction conduction

[0098] As fully described above, the circuit board according to thepresent invention comprises at least a pair of leads and a pair ofsolder bumps. The solder bumps are arranged in an adjacent relationshipand, when the solder bumps are crushed, peripheral portions of thesolder bumps are overlapped with each other. Therefore, the leadsconstructing a circuit can be easily shorted together or between them bymerely crushing the solder bumps, and the circuit can be formed into aclosed circuit.

[0099] Also, the circuit board according to the present inventioncomprises a solder bridge for electrically interconnecting landsconnected to the leads, the solder bridge being formed by the peripheralportions of the solder bumps formed on the lands, which are integrallyoverlapped with each other. Therefore, the contact area between thesolder bumps is increased and the leads can be more positively shortedbetween them.

[0100] In addition, since the peripheral portions of the solder bumpsare overlapped with each other, separation of the solder bumps isavoided, for example, even when the circuit board is bent. Therefore,the shorted state between the leads established by the solder bridge ismaintained and reliability of the circuit board can be increased.

[0101] The circuit shorting method according to the present inventioncomprises the steps of crushing one of the solder bumps such that aperipheral portion of the one solder bump is pressed or spread outwardin the radial direction to approach the other solder bump; and thencrushing the other solder bump such that a peripheral portion of theother solder bump is pressed or spread outward in the radial directionto contact with the peripheral portion of the first solder bump, wherebythe pair of leads are shorted. As a result, the circuit can bepositively formed into a closed circuit.

[0102] Also, in the circuit shorting method according to the presentinvention, the step of crushing the other solder bump is performed untila part of the peripheral portion of the other solder bump overlaps theperipheral portion of the first solder bump. Therefore, a contact areabetween the solder bumps is increased and the leads can be positivelyshorted between them.

[0103] Further, in the circuit shorting method according to the presentinvention, the solder bumps are crushed while being softened underheating. Therefore, the load required for crushing the solder bumps isreduced and the solder bumps can be positively crushed without damagingthe circuit board itself.

[0104] Moreover, in the circuit shorting method according to the presentinvention, the solder bumps are crushed simultaneously while beingsoftened under heating. Therefore, the load required for crushing thesolder bumps is reduced and the solder bumps can be positively contactedwith each other even when they are crushed simultaneously. Damage of thecircuit board is therefore avoided at the time of crushing the solderbumps.

[0105] Additionally, in the circuit shorting method according to thepresent invention, the solder bumps are each crushed under heating andrubbing. Therefore, each solder bump is pressed or spread in the planardirection of the circuit board while being crushed, and the solder bumpscan be more positively contacted with each other.

[0106] In the magnetic head according to the present invention, a sliderincluding an MR magnetic head device is attached to a fore end of a loadbeam, the above-mentioned circuit board is attached to an opposite endof the load beam, and a pair of lead lines extended from the MR magnetichead device are connected to the circuit board. The MR magnetic headdevice, the lead lines and the leads cooperate to construct or form acircuit. A pair of solder bumps connected to the leads are then crushedsuccessively to be contacted with each other, whereby the leads areshorted together or between them and the circuit is formed into a closedcircuit. As a result, the MR magnetic head device can be protectedagainst electrostatic breakdown.

[0107] Also, the magnetic head according to the present inventionincludes a circuit board which comprises at least a solder bridge forelectrically interconnecting lands connected to the leads, the solderbridge being formed by peripheral portions of the solder bumps formedrespectively on the leads and overlapped with each other. Therefore, thecontact area between the solder bumps is increased and the leads can bepositively shorted together or between them so that the circuitincluding the MR magnetic head device is formed into a closed circuit.

[0108] In addition, since the peripheral portions of the solder bumpsare overlapped with each other, separation of the solder bumps isavoided, for example, even when the circuit board is bent. Therefore,the shorted state between the leads established by the solder bridge ismaintained to prevent electrostatic breakdown of the MR magnetic headdevice, and reliability of the circuit board can be increased.

[0109] Furthermore, with the method of manufacturing a magnetic headaccording to the present invention, the circuit including the MRmagnetic head device can be easily formed into a closed circuit bymerely crushing the solder bumps, and the MR magnetic head device can beprotected against electrostatic breakdown.

What is claimed is:
 1. A circuit board comprising at least a pair ofleads for constructing a circuit, lands connected respectively to saidpair of leads, and solder bumps formed respectively on said lands,wherein said solder bumps are arranged in an adjacent relationship and,when said solder bumps are crushed, peripheral portions of said solderbumps are spread to overlap with each other.
 2. A circuit boardcomprising at least a pair of leads for constructing a circuit, landsformed for connection respectively to said pair of leads, and a solderbridge for electrically interconnecting said lands, wherein said solderbridge is formed by peripheral portions of solder bumps formedrespectively on said leads and overlapped with each other.
 3. A circuitboard according to claim 2, wherein said solder bridge is formed bycrushing said solder bumps formed respectively on said lands to anextent that crushed peripheral portions of said solder bumps areoverlapped with each other.
 4. A circuit shorting method for a circuitboard comprising at least a pair of leads for constructing a circuit,lands connected respectively to said pair of leads, and solder bumpsformed respectively on said lands and positioned adjacent to each other,said method comprising the steps of: crushing a first solder bump suchthat a peripheral portion of the first solder bump is spread outward ina radial direction to approach a second solder bump; and crushing thesecond solder bump such that a peripheral portion of the second solderbump is spread outward in a radial direction to contact with theperipheral portion of the first solder bump, whereby said pair of leadsare shorted.
 5. A circuit shorting method according to claim 4, whereinsaid step of crushing the second solder bump is performed until a partof the peripheral portion of the second solder bump overlaps theperipheral portion of the first solder bump.
 6. A circuit shortingmethod according to claim 4, wherein said first and said second solderbumps are each crushed under heating.
 7. A circuit shorting methodaccording to claim 4, wherein said first and said second solder bumpsare each crushed under heating and rubbing.
 8. A circuit shorting methodaccording to claim 5, wherein said first and said second solder bumpsare each crushed under heating.
 9. A circuit shorting method accordingto claim 5, wherein said first and said second solder bumps are eachcrushed under heating and rubbing.
 10. A magnetic head in which a sliderincluding an MR magnetic head device is attached to a fore end of a loadbeam, a circuit board is attached to an opposite end of said load beam,and a pair of lead lines extended from said MR magnetic head device areconnected to said circuit board, said circuit board comprising at leasta pair of leads connected respectively to said lead lines andconstructing a circuit including said MR magnetic head device incooperation with said lead lines, lands connected respectively to saidleads, and solder bumps formed respectively on said lands, wherein saidsolder bumps are arranged in an adjacent relationship and, when saidsolder bumps are crushed, peripheral portions of said solder bumps arespread so as to overlap with each other.
 11. A magnetic head in which aslider including an MR magnetic head device is attached to a fore end ofa load beam, a circuit board is attached to an opposite end of said loadbeam, and a pair of lead lines extended from said MR magnetic headdevice are connected to said circuit board, said circuit boardcomprising at least a pair of leads connected respectively to said leadlines and constructing a circuit including said MR magnetic head devicein cooperation with said lead lines, lands connected respectively tosaid leads, and a solder bridge for electrically interconnecting saidlands, wherein said solder bridge is formed by peripheral portions ofsolder bumps formed respectively on said leads and overlapped with eachother.
 12. A magnetic head according to claim 11, wherein said solderbridge is formed by crushing said solder bumps formed respectively onsaid lands to an extent that crushed peripheral portions of said solderbumps are overlapped with each other.
 13. A method of manufacturing amagnetic head in which a slider including an MR magnetic head device isattached to a fore end of a load beam and a circuit board is attached toan opposite end of said load beam, said circuit board comprising atleast a pair of leads connected to said MR magnetic head device, landsconnected respectively to said pair of leads, and solder bumps formedrespectively on said lands and positioned adjacent to each other, saidmethod comprising the steps of: crushing a first solder bump such that aperipheral portion of the first solder bump is spread outward in aradial direction to approach a second solder bump; and crushing thesecond solder bump such that a peripheral portion of the second solderbump is pressed to spread outward in a radial direction to contact withthe peripheral portion of the first solder bump, whereby said pair ofleads are shorted.
 14. A method of manufacturing a magnetic headaccording to claim 13, wherein said step of crushing the second solderbump is performed until a part of the peripheral portion of the secondsolder bump overlaps the peripheral portion of the first solder bump.15. A method of manufacturing a magnetic head according to claim 13,wherein said first and said second solder bumps are each crushed underheating.
 16. A method of manufacturing a magnetic head according toclaim 13, wherein said first and said second solder bumps are eachcrushed under heating and rubbing.
 17. A method of manufacturing amagnetic head according to claim 14, wherein said first and said secondsolder bumps are each crushed under heating.
 18. A method ofmanufacturing a magnetic head according to claim 14, wherein said firstand said second solder bumps are each crushed under heating and rubbing.